ProPublica spent years gathering data to shed light on how debt collectors use the courts. Today, we run through the most important lessons we learned about a tactic that affects millions.

Millions of Americans live with the possibility that, at any moment, their wages or the cash in their bank accounts could be seized over an old debt. It’s an easily ignored part of America’s financial system, in part due to a common attitude that people who don’t pay their debts deserve what’s coming to them.

A couple of years ago, we set out to find out more about the growing use of the courts to collect consumer debts. How many lawsuits are filed? Who is filing them? Who is getting sued?

The suits are filed in state and local courts, and many states rely on antiquated systems or only keep data at the county level. We ultimately collected what…